Biomimetic mercury immobilization by selenium functionalized polyphenylene sulfide fabric

Highly efficient decontamination of elemental mercury (Hg0) remains an enormous challenge for public health and ecosystem protection. The artificial conversion of Hg0 into mercury chalcogenides could achieve Hg0 detoxification and close the global mercury cycle. Herein, taking inspiration from the bio-detoxification of mercury, in which selenium preferentially converts mercury from sulfoproteins to HgSe, we propose a biomimetic approach to enhance the conversion of Hg0 into mercury chalcogenides. In this proof-of-concept design, we use sulfur-rich polyphenylene sulfide (PPS) as the Hg0 transporter. The relatively stable, sulfur-linked aromatic rings result in weak adsorption of Hg0 on the PPS rather than the formation of metastable HgS. The weakly adsorbed mercury subsequently migrates to the adjacent selenium sites for permanent immobilization. The sulfur-selenium pair affords an unprecedented Hg0 adsorption capacity and uptake rate of 1621.9 mg g−1 and 1005.6 μg g−1 min−1, respectively, which are the highest recorded values among various benchmark materials. This work presents an intriguing concept for preparing Hg0 adsorbents and could pave the way for the biomimetic remediation of diverse pollutants.

Decontaminafion of mercury pollufion from industrial flue gases is a serious environmental, which is an urgent need to solve.This work presented biomimefic mercury immobilizafion by selenium funcfionalized polyphenylene sulfide fabric.Based on the novelty and applicability of bionic mindset, the publicafion of it might expand a new direcfion to develop efficient adsorbents in diverse environmental remediafion including mercury pollufion.Thus, I strongly recommend to publish this manuscript on Nature Communicafions after minor revisions.1.A general introducfion to the field and more detailed background specific to the research should be provided in the Abstract.2. It is suggested to first discuss the characterizafions of sorbents as prepared through in-situ and post synthesis methods before providing a diagrammafic illustrafion on this process.Thus, Figure 2 may be befter placed after Figure 5 to serve this purpose.3. TPD experiments were conducted to invesfigate the mercury species on the spent sample based on the decomposifion characterisfics of mercury compounds.Besides the decomposifion of mercury compounds, the organic PPS fabric filter will be decomposed as well.Whether the decomposifion of PPS would affect the determinafion of mercury by the mercury analyzer or cause confusion for invesfigafing mercury species? 4. The authors stated that, besides the surface coverage of selenium, the crystal form of selenium played a crucial role in mercury adsorpfion, i.e., red selenium was more efficient than black selenium.Although the selenium amount was normalized by adjusfing the adsorbent dosage to compare the mercury adsorpfion performances of different samples, the effect of surface distribufion cannot be excluded.I suggest the authors could add experiments to compare the mercury adsorpfion performance of powdery red selenium and black selenium to further support the above interpretafion.5.The Se/PPS displayed a mercury recovery feature owing to its ultra-high mercury adsorpfion capacity.However, the authors did not explain how mercury was recovered from the Se/PPS, and what is the mercury recovery rafio?6.The authors stated that the Se/PPS displayed ultralong-term real applicafion potenfial.So, the mercury adsorpfion curve of Se/PPS should be provided, and the service lifefime when adopfing in a fixed bed should be evaluated.7. Whether the selenium on Se/PPS would be easily to fall off by flue gas during long-term applicafion, since the fall off of selenium not only affecfing the mercury removal performance but also cause selenium pollufion?8. Whether the parficulate mafter in flue gas would cover the acfive sites (i.e., selenium), thus hindering the mercury removal performance of Se/PPS? 9.The authors adopted the pseudo-first-order and pseudo-second-order kinefic models to simulate the mercury adsorpfion behavior, but the kinefic models were not present in the manuscript.

Reviewer #2 (Remarks to the Author):
A brand-new method was developed in this work to achieve the efficient capture of Hg0 from industrial flue gas.The most impressive novelty of this work is that it mimics the Hg0 detoxificafion mechanism in human body, which has hardly been proposed in previous studies.The novelty of this work thus makes it suitable to be published on Nature Communicafions.I believe it can significantly extend the research horizons and raise wide research interests in related fields.The results are somehow interesfing, but there are some notes that the authors have to pay aftenfion.The work is recommended to publish after a minor revision.Specific suggesfions are as follows.
(1) Please provide experimental details.For instance, how to obtain the spent sample for XPS and TPD tests?The sorbent dosage, flue gas atmosphere and flue gas temperate should be also described clearly for each set experiment, since the Hg0 adsorpfion efficiency was dependent on these experimental parameters.
(2) DTA curves should be added accompany with TG curve to befter illustrate the thermal stability of the Se/PPS.
(3) The Se/PPS was designed to be adopted in a fixed-bed reactor like filter bag type dust collector to achieve simultaneous removal of parficulate mafters and mercury from flue gas.A scheme for Hg0 removal by Se/PPS was suggested to be provided.(4) A comparafive table should be provided to demonstrate the superior performance of Se/PPS compared to other sulfur/selenium funcfionalized substrates in removing Hg0, further proving the advanced nature of the biomimefic approach.
(5) At the current stage, the preparafion parameters of the adsorbents are not clear.The author must specify the dosage of each precursor in the adsorbent preparafion secfion to ensure the reproducibility of this work.(6) The characterizafion of the adsorbent can be moved to the main content of the manuscript instead of placing it in the supplementary informafion.Addifionally, specific condifions used to obtain characterizafion results can be further specified to support the reproducibility of this work.(7) In this work, the characterizafion of adsorbents for Hg0 removal performance seems to be primarily based on the Hg0 removal efficiency and Hg0 adsorpfion capacity presented in this study.However, the authors only provide the calculafion method for Hg0 adsorpfion capacity.Please add the calculafion method for Hg0 removal efficiency.(8) Due to the ability of sulfur in PPS to adsorb Hg0, it is unclear whether there is sfill mercury sulfide present after adsorpfion saturafion.I suggest that the authors further invesfigate the mercury species on Se/PPS with depleted selenium sites through long-term mercury pretreatment to firmly establish the role of sulfur in facilitafing the immobilizafion of mercury on selenium through transport proteins.(9) The conclusion secfion mainly provides some general comments on this work.Please provide more quanfitafive descripfions of the main findings of this study in the conclusion secfion.
In this work, the authors proposed a new strategy for mercury decontaminafion from industrial flue gas, a serious task for public health and environmental sociefies.The results and the mechanism in this study are reasonable.The manuscript can be accepted after revision.Some comments are listed as follows: 1. Please avoid the use of exaggerated words like "significantly", "excellent", "obvious", etc. because the Nature Communicafions is a journal valuing scienfific expressions.2. The Abstract menfioned that the Hg0 adsorpfion capacity and adsorpfion rate of the Se/PPS are record-breaking high values.More data from previous literatures should be included to thoroughly demonstrate the superiority of the resultant Se/PPS.Moreover, the test condifions including sorbent dosage, Hg0 concentrafion and test fime should be presented when comparing the Hg0 adsorpfion capacity and adsorpfion rate.3. The powdery selenium was adopted as a reference to compare the Hg0 adsorpfion efficiency with Se/PPS.Whether the powdery selenium was a commercial sample?If so, the powdery selenium prepared with the same method adopted in this work should be prepared and the Hg0 adsorpfion efficiency of it should be tested.4. What is the dosage of powdery selenium adopted for Hg0 adsorpfion test (shown in Figure 6A), and what is the level compared with the amount of selenium on Se/PPS?It should be noteworthy that the samples were in different forms (i.e., powder and monolith).Thus, same amount of selenium should be adopted when comparing the Hg0 adsorpfion performance.5.The Se/PPS displayed a mercury recovery feature owing to its great Hg0 enrichment capacity.Mercury was recovered by decomposing the mercury adsorpfion products (i.e., HgSe) at high temperature.What is the decomposifion temperature for mercury recovery.The volafile selenium would be released accompanying with the decomposifion of HgSe at high temperature demonstrafing by the TG results.Thus, how to dispose the released selenium since it is also an atmosphere pollutant.6.The stable Hg0 adsorpfion performances under harsh condifions were crucial for real-world applicafion.The authors stated that the Se/PPS displayed excellent anfi-interference ability to general detrimental flue gas components (e.g., SO2 and H2O).The detrimental role of these flue gas components in Hg0 adsorpfion might be indeed inapparent during a short experiment fime.However, the material was designed to be adopted in a fix-bed reactor, the service fime would be generally several months.Thus, I commend the authors could conduct the Hg0 adsorpfion test with high SO2 and H2O concentrafion to further solid the above statement.7. The pseudo-first and pseudo-second kinefic models were adopted to simulate the Hg0 adsorpfion behaviors over Se/PPS.Other kinefic models like intra-parficle diffusion model and elovich model were recommended to be adopted to further invesfigate the Hg0 adsorpfion process.8.The mercury decomposifion characterisfic of Hg-laden PPS invesfigated by TPD experiment was described in lines Hg-TPD product of Hg desorpfion on PPS has been described earlier in lines 212-217, but the results were described again in the subsequent reacfion mechanism analyses.Thus, it is suggested to reorganize the relevant discussion. 1

Detailed Response to Reviewers
Reviewer #1 Decontamination of mercury pollution from industrial flue gases is a serious environmental, which is an urgent need to solve.This work presented biomimetic mercury immobilization by selenium functionalized polyphenylene sulfide fabric.Based on the novelty and applicability of bionic mindset, the publication of it might expand a new direction to develop efficient adsorbents in diverse environmental remediation including mercury pollution.Thus, I strongly recommend to publish this manuscript on Nature Communications after minor revisions.

Comment 1:
A general introduction to the field and more detailed background specific to the research should be provided in the Abstract.
We thank the reviewer for this insightful suggestion.A sentence offering a general introduction to the field and a sentence with more detailed background specific to the research has been added to the Abstract (please refer to the Abstract section in page 2).The same sentences are shown below for your reference.
'Highly efficient decontamination of elemental mercury (Hg 0 ) remains an enormous challenge for public health and ecosystem protection.The artificial conversion of Hg 0 into mercury chalcogenides could achieve Hg 0 detoxification and close the global mercury cycle.'

Comment 2:
It is suggested to first discuss the characterizations of sorbents as prepared through in-situ and post synthesis methods before providing a diagrammatic illustration on this process.Thus, Figure 2 may be better placed after Figure 5 to serve this purpose.
We thank the reviewer for this valuable suggestion.Fig. 2 has been placed after Fig. 5 to diagrammatically illustrate the assembly process and structural properties of Se/PPS after discussing the sample characterizations.Related discussions have been correspondingly revised (please refer to the 2 nd paragraph in page 9 and 1 st paragraph in page 10).The same revised discussion is shown below for your reference.
'Based on the above characterization data, the formation of Se/PPS-P and Se/PPS-I is illustrated in Fig. 5.The post synthetic process was started by coating a suspension of selenium particles, and deposition on PPS was realized via random collisions (Fig. 5a).As a result, only sparse and patchy selenium particles appeared on the Se/PPS prepared by the post synthetic method.In this scenario, even if Hg 0 was weakly adsorbed on the PPS, there were insufficient selenium ligands to bind mercury that migrated from the sulfur sites.The weakly adsorbed mercury might be discharged from the PPS into the flue gas.The in situ synthetic method (Fig. 5b) overcame these drawbacks, and SeO3 2-was first anchored on PPS to serve as a selenium precursor, and then was reduced to elemental selenium by a reductant (i.e., GSH) under alkaline conditions.The electrostatically directed assembly of selenium on PPS was realized due to the adverse ESP distribution derived from well-organized adsorption of SeO3 2-onto the PPS.Rational adjustment of the population density and the selenium distribution was achieved by adjusting the SeO3 2-and NaOH concentrations (Fig. 5c), thus providing adequate selenium for binding mercury.'

Comment 3:
TPD experiments were conducted to investigate the mercury species on the spent sample based on the decomposition characteristics of mercury compounds.Besides the decomposition of mercury compounds, the organic PPS fabric filter will be decomposed as well.Whether the decomposition of PPS would affect the determination of mercury by the mercury analyzer or cause confusion for investigating mercury species?
We thank the reviewer for this great comment.The decomposition characteristics of pure HgSe and HgS compounds mixing with PPS (without loading mercury) have been added in the revised supplementary materials and denoted as Supplemental Fig. 13 (the same figure is shown below for your reference).As shown, the mercury decomposition characteristics were very close regardless of including PPS.This demonstrates that the decomposition of PPS did not cause confusion in investigating the mercury species on the spent Se/PPS.Additionally, the mercury analyzer ran steadily when including PPS decomposition components in the carrier gas.Thus, possible interference from PPS decomposition on the measurements of the mercury analyser have been first excluded before the TPD experiments.Related discussions have been added in the revised manuscript (please refer to the 2 nd paragraph on page 10).

Stability of mercury analyzer with PPS decomposition components in the carrier gas Comment 4:
The authors stated that, besides the surface coverage of selenium, the crystal form of selenium played a crucial role in mercury adsorption, i.e., red selenium was more efficient than black selenium.
Although the selenium amount was normalized by adjusting the adsorbent dosage to compare the mercury adsorption performances of different samples, the effect of surface distribution cannot be excluded.I suggest the authors could add experiments to compare the mercury adsorption performance of powdery red selenium and black selenium to further support the above interpretation.
We thank the reviewer for this constructive suggestion.We have added experiments to compare the mercury adsorption performance of powdery red selenium and black selenium to further demonstrate the variation of different selenium crystal forms in Hg 0 adsorption.In this scenario, the interference of selenium surface distribution on Se/PPS was excluded.The results have been added in the revised supplementary materials and denoted as Supplemental Fig. 16 (the same figure is shown below for your reference).The experimental results confirmed the role of crystal form of selenium in Hg 0 adsorption, i.e., the red selenium was more active than black selenium in Hg 0 adsorption.Related discussions on this observation have been added in the 2 nd paragraph on page 11.The same revised discussion is shown below for your reference.
'This suggested that in addition to the surface coverage, the crystalline form of the selenium played a crucial role in Hg 0 adsorption, i.e., red selenium was more active in Hg 0 adsorption than black selenium.The varied Hg 0 adsorption capacities of powdery red selenium and black selenium confirmed this interpretation (shown in Supplemental Fig. 16).'

Hg 0 adsorption performances of powdery red and black selenium Comment 5:
The Se/PPS displayed a mercury recovery feature owing to its ultra-high mercury adsorption capacity.However, the authors did not explain how mercury was recovered from the Se/PPS, and what is the mercury recovery ratio?
We thank the reviewer for this valuable comment.The recovery of mercury from spent Se/PPS was conducted by thermal decomposition and condensing collection, which was realized on a device capable of rapidly decomposing mercury adsorption products to gaseous Hg 0 and then condensed to liquid mercury for collection.To better illustrate the mercury recovery process, the schematic diagram of mercury recovery system has been added in the revised supplementary materials and denoted as Supplemental Fig. 23 (the same figure is shown below for your reference).The decomposition temperature was set as 300 °C in this work, which was determined by the TPD experimental result, i.e., the mercury on the spent Se/PPS was decomposed from 150 to 300 °C according to the TPD curve.
The spent Se/PPS was placed at a furnace maintaining at 300 °C to decompose the mercury into gaseous Hg 0 .The released Hg 0 was condensed to liquid mercury in an ice-bath for collection.About 87% mercury on the spent Se/PPS can be recovered by such a strategy.Related experimental methods and discussions have been added in the revised manuscript (the 2 nd paragraph on page 15 and the 1 st paragraph on page 16) and the revised supplementary materials (the 1 st paragraph on page S6).The same revised discussion is shown below for your reference.

'Mercury and selenium recovery
The recovery of mercury from spent Se/PPS was conducted using a device capable of rapidly decomposing mercury adsorption products to gaseous Hg 0 , which was then condensed to liquid mercury for collection (as illustrated by Supplemental Fig. 23).The decomposition temperature was determined by a TPD experiment, i.e., the temperature which could guarantee the full decomposition of mercury from spent Se/PPS.The spent Se/PPS was placed at a furnace to decompose the mercury adsorption products (i.e., HgSe), and the gaseous Hg 0 was condensed to liquid mercury in an ice-bath.
Meanwhile, the selenium on Se/PPS would be released accompanying with the decomposition of HgSe.Thus, both mercury and selenium were condensed for recovery based on their different saturated vapor pressure.''The enriched mercury on Se/PPS-I can be recovered as liquid mercury metal with a device capable of rapidly decomposing mercury compounds and efficiently separating liquid mercury (shown in Supplemental Fig. 23).Specifically, the decomposition temperature was set as 300 °C based on the TPD results, i.e., the mercury on the spent Se/PPS-I was decomposed to gaseous Hg 0 in the temperature range 150-300 °C.The gaseous Hg 0 was condensed to liquid mercury in an ice bath for collection (shown in Supplemental Fig. 24a).Approximately 87% mercury on the spent Se/PPS-I was recovered with this strategy.The selenium released during the decomposition of mercury was also condensed for recovery based on the variations in saturated vapour pressures (shown in Supplemental

Comment 6:
The authors stated that the Se/PPS displayed ultralong-term real application potential.So, the mercury adsorption curve of Se/PPS should be provided, and the service lifetime when adopting in a fixed bed should be evaluated.
We thank the reviewer for this valuable suggestion.The Hg 0 adsorption curve of Se/PPS has been added in the revised manuscript and supplementary materials (please refer to Fig. 7e and Supplemental Fig. 22).The same figures are shown below for your reference.According to the saturated Hg 0 adsorption capacity and the adsorption breakthrough curve, the service time of Se/PPS when adopted in a typical coal-fired flue gas condition was estimated.Related discussions have been added to the manuscript (please refer to the 2 nd paragraph in page 15).The same revised discussion is shown below for your reference.
'A large Hg 0 adsorption capacity was crucial for practical application of the monolithic Se/PPS-I in a fixed-bed since ultralong-term stability would prolong the service life and avoid frequent adsorbent replacement.As shown in Fig. 7e, almost no Hg 0 was detected at the adsorbent bed outlet over 70 h with a specific gas flow rate of 1.13 m min -1 , even though the inlet Hg 0 concentration was as high as 1000 µg m -3 .The Hg 0 adsorption capacity of Se/PPS-I was 1203.4 mg g -1 when reaching 80% breakthrough (shown in Supplemental Fig. 22).Additionally, the adsorption rate was calculated as 1005.6 μg g −1 min −1 .This Hg 0 adsorption capacity and rate are the highest recorded values among various materials (shown in Fig. 7f and Supplemental Table S2) 14, 19, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51 .Based on the saturated Hg 0 adsorption capacity and the adsorption breakthrough curve, the Hg 0 concentration in coal-fired flue gas is expected to be reduced from approximately 20 µg m -3 to below 1.7 µg m -3 (i.e., the current most rigorous emission limit in the world) for 9940 h if Se/PPS-I was used with a real specific gas flow rate of 0.8 m min -1 .'Whether the selenium on Se/PPS would be easily to fall off by flue gas during long-term application, since the fall off of selenium not only affects the mercury removal performance but also causes selenium pollution?
We thank the reviewer for this insightful comment.We have tested the content of selenium lost from Se/PPS purging with N2 for 14 days so as to confirm the stability of selenium during long-term application.The results have been added in the supplementary materials and denoted Supplemental Fig. 11 (the same figures are shown below for your reference).As shown, the weight change of Se/PPS after purging with N2 for 14 days could be negligible.Meanwhile, we have determined the selenium content on the Se/PPS purging with N2 for 14 days by inductively coupled plasma mass spectrometry.The selenium content on the purged Se/PPS was 2.81%, which was very close to that on the fresh Se/PPS (2.83%).This could fully demonstrate that selenium was firmly anchored on the PPS.Accordingly, the fall off of selenium during long-term application was insignificant in affecting the Hg 0 adsorption performance and causing selenium pollution.Related experimental methods and discussions have been added in the revised manuscript (1 st paragraph on page 8) and the revised supplementary materials (2 nd paragraph on page S3).

The weight change of Se/PPS purging with N2 for 14 days
The selenium content of Se/PPS before and after purging with N2 for 14 days (determined by inductively coupled plasma mass spectrometry)

Comment 8:
Whether the particulate matter in flue gas would cover the active sites (i.e., selenium), thus hindering the mercury removal performance of Se/PPS?
We thank the reviewer for this valuable comment.We have added experiments to investigate the effect of particulate matter on the Hg 0 removal performance of Se/PPS.The Se/PPS was firstly covered by particulate matter (i.e., fly ash) collected from a coal-fired power plant, and then the Hg 0 removal performance was tested.The result has been added to the revised supplementary materials and denoted as Supplemental Fig. 21 (the same figure is shown below for your reference).As shown, very close Hg 0 removal performances of Se/PPS with and without covering by particulate matter were obtained.
Thus, the inhibitive effect of particulate matter on the Hg 0 removal performance of Se/PPS can be negligible.Related discussions have also been added in the revised manuscript (please refer to the 1 st paragraph in page 15).The same revised discussion is shown below for your reference.
'The excellent performance of Se/PPS-I at 100-150 °C (Fig. 6e) implied that Se/PPS-I could serve as a dust filter bag material to achieve simultaneous removal of particulate matter and Hg 0 from flue gases, as illustrated in Supplemental Fig. 20.Supplemental Fig. 21 shows that the Hg 0 removal capacities of Se/PPS with and without coverage by particulate matter were similar, implying feasibility for long-term use under high-concentration dust conditions.'The authors adopted the pseudo-first-order and pseudo-second-order kinetic models to simulate the mercury adsorption behavior, but the kinetic models were not present in the manuscript.
We thank the reviewer for this great reminder.The kinetic models have been added in the revised supplementary materials (please see page S6 and page S7).Other typical kinetic models including Intra-particle diffusion model and Elovich model have been also adopted to further investigate the Hg 0 adsorption behaviors over Se/PPS.The same kinetic modes are shown below for your reference.

Pseudo-first-order model
This model is based on the mass balance.The Hg adsorption rate was proportional to the difference between the equilibrium capacity and the adsorbed amount at any time, as described following: (1) Equation ( 1) could be modified to the following equation based on the initial conditions of t=0 qt=0 and t=t qt=qt,: ( where qt and qe represent the adsorbed mercury amount at any time t and equilibrium time (µg⋅g -1 ).k1 represents the rate constant (min -1 ).qe and k1 can be attained by fitting the adsorption curve.

Pseudo-second-order model
The pseudo-second-order model represents that the surface diffusivity is inversely proportional to the square of concentration variation on sorbent surface, which could be described as following: (3) Equation ( 1) can be modified to the following equation based on the initial conditions of t=0 qt=0 and t=t qt=qt,: (4) where k2 represents the rate constant (min -1 ).The term k2qe 2 was the initial adsorption rate.

Intra-particle diffusion model
The Intra-particle diffusion model assumes that the intra-particle diffusivity is constant and the diffusion direction is radial.The model can be interpreted by the following equation: 13 (6) where kid represents the intraparticle diffusion rate constant, C is proportional to the boundary layer.

Elovich model
The Elovich model assumes that sorption takes place in two phases: (1) a fast initial reaction associated with the movement of the sorbate to external sites, (2) a slower diffusion in and out of the microspores over sorbent.This model can be described by the following equation: (7) where α represents the initial rate, β is related to the extent of surface coverage and activation energy for chemisorption.If t is much larger than t0 this equation is modified as follows: (8) '

Reviewer #2
A brand-new method was developed in this work to achieve the efficient capture of Hg 0 from industrial flue gas.The most impressive novelty of this work is that it mimics the Hg 0 detoxification mechanism in human body, which has hardly been proposed in previous studies.The novelty of this work thus makes it suitable to be published on Nature Communications.I believe it can significantly extend the research horizons and raise wide research interests in related fields.The results are somehow interesting, but there are some notes that the authors have to pay attention to.The work is recommended to publish after a minor revision.Specific suggestions are as follows.

Comment 1:
Please provide experimental details.For instance, how to obtain the spent sample for XPS and TPD tests?The sorbent dosage, flue gas atmosphere and flue gas temperate should be also described clearly for each set experiment, since the Hg 0 adsorption efficiency was dependent on these experimental parameters.
We thank the reviewer for this valuable suggestion.The sample pretreatment method for XPS and TPD tests has been added in page S4 of the revised supplementary materials.A table for summarizing the experimental conditions including flue gas atmosphere, flue gas temperate, gas hourly space velocity (GHSV) have been also presented in the revised supplementary materials and denoted as Table S1 (the same table is shown below for your reference).DTA curves should be added to accompany with TG curve to better illustrate the thermal stability of the Se/PPS.

Experiments
We thank the reviewer for this insightful suggestion.DTA curves have been added to accompany with TG curve in the revised manuscript and denoted as Fig. 4a and Supplemental Fig.A comparative table should be provided to demonstrate the superior performance of Se/PPS compared to other sulfur/selenium functionalized substrates in removing Hg 0 , further proving the advanced nature of the biomimetic approach.
We thank the reviewer for this valuable suggestion.A comparison We thank the reviewer for this great reminder.We have clearly described the sample preparation parameters to ensure the reproducibility of this work (please refer to pages S2 and S3 of the supplementary materials).The same revision is shown below for your reference.
'The in-situ synthesis procedure for Se/PPS was as follows.First, 2.6 mmol sodium selenite (Na2SeO3) was fully dissolved in deionized water and stirred for 0.5 h.Then, a piece of commercially purchased PPS fabrics (6 g) was immersed in the solution and oscillated for 6 h continuously.After that, 5.85 mmol glutathione (GSH, reduced form) was added into the solution and oscillated for another 6 h.Then, 12.5 mmol sodium hydroxide (NaOH) solution was dropwise added into the suspension to bring the pH above 12 and oscillated for 5 h at room temperature.Finally, the product was rinsed with deionized water before drying at 110 °C for 12 h.The as-prepared sample is denoted as Se/PPS-I.The dosage of selenium precursor and NaOH was also adjusted to synthesize Se/PPS-I samples with various Se coating mounts and morphologies.Polyester fabric without containing sulfur was also adopted to be functionalized by the in-situ synthesis method (denoted as Se/Polyester).In addition, the SeO3 2-loaded PPS (denoted as SeO3 2-/PPS) was prepared by the same procedure for obtaining Se/PPS-I but without adding GSH and NaOH.
As a reference, the post synthesis method was adopted to prepare Se/PPS-P.First, a suspension containing selenium particles was prepared by dissolving 2.6 mmol of Na2SeO3, 5.85 mmol of GSH, and 12.5 mmol of NaOH in deionized water and stirring for 5 h.Then, a piece of PPS fabric (6 g) was immersed in the solution and oscillated for 5 h continuously.Finally, the product was rinsed with deionized water several times and dried at 110 °C for 12 h.The dosages of selenium precursor and NaOH were the same as those for preparing Se/PPS-I samples.
The powdery selenium preparation procedure was same as that for Se/PPS but only without containing PPS.Specifically, 2.6 mmol Na2SeO3 was fully dissolved in deionized water and stirred for 0.5 h.After that, 5.85 mmol GSH (reduced form) was added into the solution and oscillated for another 6 h.Then, 12.5 mmol NaOH solution was dropwise added into the suspension to bring the pH above 12 and oscillated for 5 h at room temperature.Finally, the powdery selenium sample was obtained after centrifuging, rinsing with deionized water, and drying at 110 °C for 12 h.'

Comment 6:
The characterization of the adsorbent can be moved to the main content of the manuscript instead of placing it in the supplementary information.Additionally, specific conditions used to obtain characterization results can be further specified to support the reproducibility of this work.
We thank the reviewer for this valuable suggestion.We have moved the characterization results and related discussion to the main content of the manuscript (please refer to Figure 7 and Supplemental Fig. 19, the 2 nd paragraph in page 14 and 1 st paragraph in page 15).The same revision is shown below for your reference.
'Since Se/PPS-I was designed for use with different industrial flue gases, the Se/PPS-I should withstand harsh operating conditions.As shown in Fig. 7a, Se/PPS-I did not exhibit interference from typical flue gas components, including H2O, SO2 and particulate matter.The water contact angle above 130° indicated the hydrophobicity of Se/PPS-I (shown in Fig. 7b).As a result, the likelihood of H2O covering the selenium surface was diminished, thus eliminating the adverse effect of H2O on Hg 0 adsorption.Additionally, there were no obvious changes in the oxidation states of Se and S on the 'The Hg 0 adsorption capacity and Hg 0 removal efficiency were calculated by the following equations.
where Q is the Hg 0 adsorption capacity ( mg Hg•g -1 adsorbent),  is the Hg 0 removal efficiency (%), A is the volume of sorbent (m 3 ), f is the gas flow rate (m 3 h -1 ), t is the accumulated time of every set experiment (h) and t=120 min when calculating the adsorption efficiency, Cin and Cout is the inlet and outlet Hg 0 concentration (µg m -3 ).'

Comment 8:
Due to the ability of sulfur in PPS to adsorb Hg 0 , it is unclear whether there is still mercury sulfide present after adsorption saturation.I suggest that the authors further investigate the mercury species on Se/PPS with depleted selenium sites through long-term mercury pretreatment to firmly establish the role of sulfur in facilitating the immobilization of mercury on selenium through transport proteins.
We thank the reviewer for this insightful comment.We have conducted two sets of additional experiments to clarify the role of sulphur in facilitating the immobilization of mercury.
First, we compared the Hg 0 removal performances of polyester, PPS, Se/polyester, and Se/PPS.The two supporters (polyester and PPS) as adopted shared similar tangled structures, while polyester contains no sulphur ligand.The results have been added in the supplementary materials and denoted Supplemental Fig. 17 (the same figures are shown below for your reference).As shown, when raising the reaction temperature, the Hg 0 removal performances of PPS improved, but the Hg 0 removal performance of polyester was slightly compromised.This phenomenon indicates that Hg 0 adsorption in PPS was primarily attributed to chemical interaction in the presence of sulfur ligands, because chemical interaction can be improved by higher reaction temperature with more energy input.
However, for polyester, the physisorption effects might dominate, and higher temperature caused the desorption of physiosorbed products.The observations indicate that, in the absence of Se, Hg 0 might chemically interact with sulfur ligands in PPS at relatively high temperature.Such chemical interaction was further supported by another controlled set of experiment between Se/polyester and Se/PPS.As shown in the following figure, Se/polyester and Se/PPS exhibited comparable Hg 0 removal performances at temperatures lower than 75 o C, which suggests that, before chemical interaction between mercury and sulphur was adequately activated, Se/polyester and Se/PPS did not vary in Hg 0 removal capacity.Contrarily, when the reaction temperature raised to higher than 75 o C, a temperature coincided with the activation temperature of chemical interaction, Se/PPS significantly outperformed Se/polyester for Hg 0 capture.The above-mentioned observations are performance proof of the faciliting role of sulphur ligands in promoting the Hg 0 removal on Se/PPS.was ascribed to mercury-selenium interaction (i.e., HgSe) because this peak did not occur in the TPD pattern of Hg-laden PPS.It was found that no characteristic peak accounting for mercury-PPS interaction was observed in unsaturated Se/PPS-I because, when the sample was far from being saturacted, and the amount of active selenium was abundant in the sample, mercury interacted with PPS supporter, if any, would be immediately transferred to mercury selenide on the surface of Se/PPS-I.However, if we increased the pretreatment time and consumed most of the active selenium sites in Se/PPS-I, the interaction between PPS and mercury could be observed, which was manifested by the occurrence of 160 o C peak in the saturated Se/PPS-I (adsorption of Hg 0 for more than 50 h).This characteristic proof further supports that the PPS-sulphur did interact with mercury, and the absence of mercury-sulfur intermediates in unsaturated Se/PPS is mainly ascribed to the spontaneous and rapid transformation of the intermediates into the mercury selenide final product when selenium sites were abundant.

TPD patterns for spent PPS, Se powder plus PPS, Se/PPS (unsaturation), and Se/PPS (saturation)
The above two sets of experiments could establish the role of sulfur in facilitating the immobilization of mercury on selenium through transport carrier, i.e., Hg 0 was firstly weakly-adsorbed on sulfur and then captured by selenium for permanent immobilization as HgSe.However, since the mercury species pre-adsorbed on the sulfur in PPS would be immediately consumed, directly detecting the transition road between mercury-sulfur and mercury-selenium is extremely difficult with current techniques.Related discussions have been revised in the updated manuscript (please refer to the 2 nd and in page 16, 1 st and 2 nd paragraphs in page 17, 1 st paragraph in page 18).

Comment 9:
The conclusion section mainly provides some general comments on this work.Please provide more quantitative descriptions of the main findings of this study in the conclusion section.
We thank the reviewer for this valuable suggestion.We have rewritten the conclusion section to provide more quantitative descriptions of the main findings of this study (please refer to the 2 nd paragraph in page 19).The same revision is shown below for your reference.
'In conclusion, this work demonstrated for the first time the feasibility of enhancing Hg 0 adsorption on functionalized substrates via a biomimetic pathway.The population density, distribution, and crystalline form of selenium were rationally regulated by adjusting the concentrations of NaOH and SeO3 2-from 0% to 1% and 2.75% to 44%, respectively.At a reaction temperature higher than 100 °C, which was within the operation temperature range for fabric fibers under practical flue gas cleaning scenarios, the resultant Se/PPS-I displayed a Hg 0 adsorption capacity and uptake rate of 1621.9 mg g - 1 and 1005.6 μg g -1 min -1 , respectively.The excellent Hg 0 adsorption performance of Se/PPS-I was attributed to the plentiful sulfur sites in PPS that served as buffers for Hg 0 transport to the adjacent selenium.The resistance of Se/PPS-I to flue gas interference enables ultralong-term use under harsh flue gas conditions, and it is expected to serve for approximately 10000 h without changing the adsorbent.This work developed an effective Hg 0 adsorbent and provided guidance for biomimetic design of advanced functional filters for pollutant abatement.'

Reviewer #3
In this work, the authors proposed a new strategy for mercury decontamination from industrial flue gas, a serious task for public health and environmental societies.The results and the mechanism in this study are reasonable.The manuscript can be accepted after revision.Some comments are listed as follows:

Comment 1:
Please avoid the use of exaggerated words like "significantly", "excellent", "obvious", etc. because the Nature Communications is a journal valuing scientific expressions.
We thank the reviewer for this great reminder.We have refrained from using subjective language when referring to the scientific findings, and the related findings were described by quantitative conclusion in the revised manuscript.

Comment 2:
The Abstract mentioned that the Hg 0 adsorption capacity and adsorption rate of the Se/PPS are record-breaking high values.More data from previous literatures should be included to thoroughly demonstrate the superiority of the resultant Se/PPS.Moreover, the test conditions including sorbent dosage, Hg 0 concentration and test time should be presented when comparing the Hg 0 adsorption capacity and adsorption rate.
We thank the reviewer for this valuable suggestion.More data from previous literatures have been added in the revised manuscript to thoroughly demonstrate the superiority of Hg 0 adsorption performances of Se/PPS.Different kinds of adsorbents including sulfur/selenium functionalized materials, metal oxides, noble metals, minerals, etc., have been included for a thorough comparison.
A comparison table showing the Hg 0 adsorption performances of Se/PPS and other adsorbents has been added in the supplementary materials and denoted Table S2 23 and Fig. 24).Related experimental methods and discussions have been added in the revised manuscript (please refer to the 2 nd paragraph in page 15 and 1 st paragraph in page S6 in the supplementary materials).The same revision is shown below for your reference.
'The enriched mercury on Se/PPS-I can be recovered as liquid mercury metal with a device capable of rapidly decomposing mercury compounds and efficiently separating liquid mercury (shown in Supplemental Fig. 23).Specifically, the decomposition temperature was set as 300 °C based on the TPD results, i.e., the mercury on the spent Se/PPS-I was decomposed to gaseous Hg 0 in the temperature range 150-300 °C.The gaseous Hg 0 was condensed to liquid mercury in an ice bath for collection (shown in Supplemental Fig. 24a).Approximately 87% mercury on the spent Se/PPS-I was recovered with this strategy.The selenium released during the decomposition of mercury was also condensed for recovery based on the variations in saturated vapour pressures (shown in Supplemental Fig. 24b).'

'Mercury and selenium recovery
The recovery of mercury from spent Se/PPS was conducted using a device capable of rapidly decomposing mercury adsorption products to gaseous Hg 0 , which was then condensed to liquid mercury for collection (as illustrated by Supplemental Fig. 23).The decomposition temperature was determined by a TPD experiment, i.e., the temperature which could guarantee the full decomposition of mercury from spent Se/PPS.The spent Se/PPS was placed at a furnace to decompose the mercury adsorption products (i.e., HgSe), and the gaseous Hg 0 was condensed to liquid mercury in an ice-bath.The stable Hg 0 adsorption performances under harsh conditions were crucial for real-world applications.The authors stated that the Se/PPS displayed excellent anti-interference ability to general detrimental flue gas components (e.g., SO2 and H2O).The detrimental role of these flue gas components in Hg 0 adsorption might be indeed inapparent during a short experiment time.However, the material was designed to be adopted in a fix-bed reactor, the service time would be generally several months.Thus, I commend the authors could conduct the Hg 0 adsorption test with high SO2 and H2O concentration to further solid the above statement.
We thank the reviewer for this insightful comment and suggestion.The effects of SO2 and H2O on the Hg 0 adsorption performance of Se/PPS have been reconfirmed through conducting the Hg 0 adsorption test under high SO2 and H2O concentration, the results of which have been added in the revised manuscript and denoted Fig. 7a and Supplemental Fig. 19 (the same figure is shown below for your reference).Related experimental details and discussions have been added in the revised manuscript (the 2 nd paragraph in page 14 and the 1 st paragraph in page 15) and the supplementary materials (Table S1 and the 1 st paragraph in page S5).The same revision is shown below for your reference.
'Since Se/PPS-I was designed for use with different industrial flue gases, the Se/PPS-I should withstand harsh operating conditions.As shown in Fig. 7a, Se/PPS-I did not exhibit interference from typical flue gas components, including H2O, SO2 and particulate matter.The water contact angle above 130° indicated the hydrophobicity of Se/PPS-I (shown in Fig. 7b).As a result, the likelihood of H2O covering the selenium surface was diminished, thus eliminating the adverse effect of H2O on Hg 0 adsorption.Additionally, there were no obvious changes in the oxidation states of Se and S on the fresh and pretreated Se/PPS (shown in Fig. 7c).Thus, unlike other adsorbents reported previously, such as activated carbons, metal oxides, and noble metals, which were partially deactivated by the presence of H2O and SO2, [31] Se/PPS-I maintained stable Hg 0 adsorption in flue gases containing 20% H2O and 2% SO2 (shown in Supplemental Fig. 19).' selenium sites for permanent immobilization.As shown in Fig. 8a, the Hg-laden selenium powder + PPS (i.e., selenium powder mechanically mixed with PPS) exhibited two characteristic decomposition peaks located at ~ 160 o C and 230 o C. By comparing the Hg-TPD patterns of pristine PPS, unsaturated Se/PPS-I (adsorption of Hg 0 for 2 h), and selenium powder + PPS, it was found that the characteristic peak at ~ 160 o C was attributed to the chemical interaction between PPS-sulphur and mercury (no physisorption was accounted considering the high pretreatment and decomposition temperature), and the one centered at ~ 230 o C was ascribed to HgSe 12 .It was found that no characteristic peak accounting for mercury-PPS interaction was observed in unsaturated Se/PPS-I because, when the sample was far from being saturacted, and the amount of active selenium was abundant in the sample, mercury interacted with PPS supporter, if any, would be immediately transferred to mercury selenide on the surface of Se/PPS-I.However, if increased the pretreatment time and consumed most of the active selenium sites in Se/PPS-I, the interaction between PPS and mercury could be observed, which was manifested by the occurrence of 160 o C peak in the saturated Se/PPS-I (adsorption of Hg 0 for more than 50 h).This further supports that the PPS-sulphur did interact with mercury, and the absence of mercury-sulfur intermediates in unsaturated Se/PPS is mainly ascribed to the spontaneous and rapid transformation of the intermediates into the mercury selenide final product when selenium sites were abundant.Thus, it was speculated that the plentiful sulfur in Se/PPS-I provided bridges to intercept Hg 0 , and the weakly adsorbed mercury subsequently migrated to the selenium interfaces for permanent immobilization.'

REVIEWERS' COMMENTS
Reviewer #1 (Remarks to the Author): The present manuscript on mercury immobilizafion by Se funcfionalized PPS is highly effecfive with the highest recorded values of Hg0 adsorpfion capacity as well as uptake rate (1621.9mg•g -1 and 1005.6 ug•g -1 •min -1 ), exhibifing a disfincfive advantage than other materials.The paper is well wriften and very clear.The presentafion and analysis of results are interesfing with good comparison and well structured.I recommend accepfing the manuscript.

Reviewer #2 (Remarks to the Author):
This arficle proposed a brand-new method to achieve the efficient capture of Hg0 from industrial flue gas.Unlike previous studies, it presents a novel detoxificafion mechanism of mercury in the human body.
The nine quesfions raised during the review process have all been explained by the author with detailly and reasonably.Supplementary materials have been added, and modificafions have been made accordingly in the arficle.The work is recommended to publish on Nature Communicafions after above rivisions.

Reviewer #3 (Remarks to the Author):
The manuscript can be accepted in this state.

Fig.
Fig.24b).' (a) Hg 0 adsorption curve, and (b) Hg 0 adsorption capacity of Se/PPS-I as a function of time Comment 7: (a) Se/PPS covered by fly ash, (b) Hg 0 removal performances of Se/PPS with and without covering by fly ash Comment 9: figures are shown below for your reference.

Hg 0
adsorption performances of different samples at varied temperatures.(a) PPS, (b) Se/PPS-I, (c) Polyester, (d) Se/Polyester Second, we have conducted additional mercury temperature programmed desorption/decomposition (Hg-TPD) experiments to confirm the migration of transient mercury-sulfur species to selenium sites for permanent immobilization.The results have been added in the revised manuscript and denoted Fig.
8(a) (the same figures are shown below for your reference).Four different Hg-laden samples were prepared.Specifically, the pristine PPS and Se/PPS-I were pretreated by 1 L•min -1 N2 containing 1000 μg•m -3 Hg 0 at 125 °C for 2 or 50 h and purging by 1 L•min -1 N2 to remove the unstable mercury to obtain a mercury-laden sample.Besides, Hg-laden selenium powder mechanically mixed with PPS (i.e., selenium powder+PPS) was also used as a reference.Among the four samples, the Hg-laden selenium powder + PPS exhibited two characteristic decomposition peaks located at ~ 160 o C and 230 o C. By comparing the Hg-TPD patterns of pristine PPS, unsaturated Se/PPS-I (adsorption of Hg 0 for considering the high pretreatment and decomposition temperature), and the one centered at ~ 230 o C Photo of mercury and selenium recovered from spent Se/PPS-I.(a) liquid mercury, (b) selenium tableshowing the Hg 0 adsorption performances of Se/PPS and other adsorbents has been added in the supplementary materials and denoted TableS2(the same table is shown below for your reference).Besides sulfur/selenium functionalized materials, other typical adsorbents including metal oxides, noble metals, minerals, etc., PPS in removing Hg 0 .Related discussions have been revised in the updated manuscript (please refer to the 2 nd paragraph in page 15).At the current stage, the preparation parameters of the adsorbents are not clear.The author must specify the dosage of each precursor in the adsorbent preparation section to ensure the reproducibility of this work.
have been also included for a thorough comparison.As shown, the Hg 0 adsorption capacity of Se/PPS was the highest among all of benchmark materials.This table fully justifies the superior performance of Se/

0 adsorption capacities of different adsorbents
(the same table is shown below for your reference).The test conditions including carrier gas, Hg 0 concentration and test time have been presented in the table when comparing the Hg 0 adsorption capacity and adsorption rate.As shown, the Hg 0 adsorption capacity of Se/PPS was the highest among all of benchmark materials.This table fully justifies the superior performance of Se/PPS in removing Hg 0 .Related discussions have been revised in the updated manuscript (please refer to the 2 nd paragraph in page 15).for recovery based on their different saturated vapor pressure, as schematically illustrated by the following figure.It is observed that mercury and selenium can be deposited in the condensers and collected.The above figures have been added in the supplementary materials (please refer to Supplemental Fig.